This invention relates to an apparatus for developing a dental x-ray film which is packaged in a light-proof envelope. More particularly, this invention relates to an apparatus for developing a dental x-ray film which is packaged in a light-proof envelope having two covering surfaces, in which a tear strip is formed on the covering surfaces at an edge common to the package and the covering surfaces are joined to one another so as to be easily pulled apart at their two edges running parallel to the edge with the tear strips, the apparatus having a developing tank with a developing frame underneath an entry slot in which the dental x-ray film is to be inserted.
The commonly used dental x-ray films have long been contained in a light-proof and saliva-proof pocket-like package made of plastic together with a lead foil, a separator card and an enveloping black paper. The separator card is arranged between the lead film and the dental x-ray film so as to protect the dental x-ray film from contact with the lead foil. Otherwise the latter would produce spots on the dental x-ray film. The black paper protects against exposure to light.
When the exposed dental x-ray film is to be developed, it must first be removed from the package in a darkened room. Removal from the package of the small 30.times.40 mm dental x-ray film and smaller children's 22.times.30 mm dental x-ray film presents difficulties, for the packages are complex and of different design and not easy to open because they have to guard the film against exposure to light and against the moisture of the mouth. Furthermore, when opening the package care must be taken to free the dental x-ray film from the lead foil, the separating card and the black paper contained loose in the package before developing. Automatic removal of the dental x-ray film from the package in the case of the known packages is not possible on account of their complicated and complex configuration.
The known packages, however, not only have the disadvantage that they can be handled only with difficulty. They are also less than desirable for environmental reasons and the safeguarding of resources. Since a lead foil is present in each package, such lead foil becomes wasted upon the opening of the dental x-ray film. For reasons of cost, therefore, the lead foil is made relatively thin, but this has the disadvantage that it absorbs only 20-40% of the x-rays and therefore offers only incomplete protection against x-radiation. The outer wrapping usually consists of polyethylene and therefore, just like the lead foil, it must not be disposed of together with the separating card and the black paper. Usually, however, for reasons of convenience, the entire wrapping with the lead foil and the polyethylene is thrown into the wastepaper basket.
After the x-ray film is unwrapped, its insertion into the developing frame of the developing apparatus presents additional difficulties, because this work also must be done in the dark. Usually the dental x-ray film is clamped to a corner on the developing frame. Often, the clamping is done in the image area, so that part of the image content is lost. The developing and fixing of the dental x-ray film that follows often takes place in the known apparatus in a less than optimum manner as regards movement and temperature. Thus x-ray images of insufficient quality are often the result.
While the development of dental x-ray films is performed in many dental practices in small, darkened and sometimes poorly ventilated rooms with developing apparatus that is hard to manipulate, developing apparatus are known in microfilm technology which are compact and simple to operate, and which can operate with fixing developers. DE-B-11 46 353 is given as an example of the state of the art. This disclosure shows a developing box onto which a cassette containing the undeveloped film is placed in a light-proof manner. After the cassette is opened this film drops into a film frame and then passes into the tank. A developing apparatus of this kind, however, is not suitable for dental x-ray films, because the latter must be housed during exposure in a very shallow and, of course, low-cost package, while the films in the above-mentioned developing apparatus run from a camera into the cassette. The cassette, therefore, is not a package but a component that is to be reused again and again.
CH-A-351 495 describes a package for a dental x-ray film which is contained in a light-proof envelope which in turn is disposed within an easy-to-open external envelope.
Tear strips are described in EP-A-0 363 092 in the case of transparent envelopes for dental x-ray films.
An apparatus for developing sheet films for measuring exposure to radiation is described in DE-B-12 26 881. In the apparatus explained in this document a developing tank has a roof-shaped upper part in the peak of which is the entry slot.